CN111606541A - Method for synchronously improving and dewatering sludge excavated in urban rail transit engineering - Google Patents
Method for synchronously improving and dewatering sludge excavated in urban rail transit engineering Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
- B01D25/12—Filter presses, i.e. of the plate or plate and frame type
- B01D25/21—Plate and frame presses
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
- C02F11/145—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances using calcium compounds
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01B—PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS
- E01B2/00—General structure of permanent way
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F2209/03—Pressure
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/44—Time
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/16—Regeneration of sorbents, filters
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Abstract
The invention provides a method for synchronously improving and dehydrating sludge excavated in urban rail transit engineering, which comprises the following steps: carrying out hydration slurry adding and impurity removing treatment on the sludge to obtain slurry; weighing the modifying agent, adding water to prepare modifying agent slurry, adding the prepared modifying agent slurry into the slurry to obtain mixed slurry, uniformly stirring the mixed slurry by using a double-shaft stirrer, and standing for tempering to obtain mixed slurry; performing filter pressing dehydration on the mixed slurry by adopting a plate-and-frame filter press, and reducing the water content of the mixed slurry to obtain a mud cake, namely improved soil; and (3) standing and stacking the obtained improved soil on site or in a way of transporting to a construction part, and turning and stirring the improved soil during stacking so as to further reduce the moisture content of the improved soil. The sludge treated by the method provided by the invention can realize engineering utilization, and the treated sludge can be used for filling materials of the bottom layer of the railway foundation bed and the embankment below the foundation bed.
Description
Technical Field
The invention relates to the technical field of urban construction excavation sludge, in particular to a method for synchronously improving and dehydrating the excavation sludge in urban rail transit engineering.
Background
The coastal region is the region with most developed economy, the largest population density and the most dense cities in China, the traffic pressure of coastal cities is gradually increased along with the rapid development of economy, and in order to meet the traffic demands of the cities, rail traffic is constructed on a large scale, and has the advantages of safety, accuracy, rapidness, comfort, energy conservation and environmental protection; due to the restriction of the existing buildings, most urban rail transit lines are underground lines, the underground lines have a large number of excavation parts, rail transit engineering through silt clay and silt stratums can generate a large number of silts, and the appropriate disposal and resource utilization of the silts are difficult problems to be solved urgently. A large amount of sludge becomes public nuisance because of being incapable of being safely consumed, treated or effectively recycled, the sludge is currently treated by being transported to open sea for throwing or to be transported to a low-lying place for landfill or being specially provided with a storage yard for stacking, the ecological environment of oceans, swamps and lakes can be seriously damaged or precious land resources can be occupied and wasted by the treatment modes, and the requirements of safety, environmental protection and ecological civilization construction are not met.
The deep silt or silt clay in coastal areas has the characteristics of high clay content, high organic matter content, high water content and high compressibility, so that the engineering characteristics are extremely poor and the deep silt or silt clay cannot be directly used as engineering filler; the large-scale resource and engineering utilization of the sludge is a practical way for treating the sludge, and has great economic and social benefits.
For the research on the engineering application of the plastic sludge, due to the difficulty that materials, equipment, processes and methods cannot be coordinated, the research is stopped at the stage of experimental research on a small test piece of an improved material in a laboratory at present. The engineering property of the sludge is extremely poor, and the sludge also contains substances harmful to the conventional gelled material, so that even if the modifier consisting of the composite material is used, the generated effects such as the water content performance still cannot meet the construction requirement, and the technical indexes such as the strength and the durability of the filling body still cannot meet the design requirement. The research results on construction equipment, processes and the like for treating the sludge are few, and the existing results cannot be really used for engineering practice due to the problems of low productivity and poor economical efficiency. When the sludge is improved by adding materials such as chemical modifiers or physical modifiers (such as sand, stone, soil and the like), the basic requirement is that the materials are uniformly mixed, and the quality of a filling body can be ensured and the filling body can play a role only by uniformly mixing the modifiers and the sludge, so that the engineering significance is realized. The existing mixing technology for improving the sludge comprises the following steps: the mixing technologies of manual paving combined with excavator stirring, concrete mixer (intermittent) stirring and stabilized soil mixer (double horizontal shaft and continuous) have the defects of high pollution, inaccurate metering, uneven mixing and low efficiency, thus the requirements of engineering practice can not be met.
At present, a process method for improving sludge by adopting 'road mixing' and 'plant mixing' is adopted, and the process of the 'road mixing' is as follows: estimating the volume or the mass of the sludge on site, manually spreading bagged admixture, mixing by an excavator, firstly doping a part of consolidation agent to sand the sludge and slightly reduce the water content, then transporting the mixture to a filling part for tedding, continuously tedding the rest part of consolidation agent, smashing and uniformly mixing by using a road mixer, wherein the technology has the defects of inaccurate measurement, difficult spreading construction, nonuniform mixing, serious dust scattering pollution of curing agent or consolidation agent, low productivity and the like, and the mixture prepared by the road mixing technology has extremely poor uniformity and difficult quality guarantee; the equipment used for plant mixing is equipment similar to a concrete intermittent forced mixer or a continuous double-horizontal-shaft mixer similar to a stable soil mixer, and the equipment similar to the concrete intermittent forced mixer cannot perform blanking or quantitative feeding on high-viscosity and plastic sludge even if a charging bucket or a hopper of an automatic gate is used, cannot ensure the constant proportion of an external admixture and the sludge, and causes large mixing amount fluctuation and unsuspected quality of a consolidation agent in a mixture. The uniformity of the mixture is improved by prolonging the stirring time, so that the production capacity is extremely low, the energy consumption is extremely high, and the excavated sludge cannot be treated in a large scale and at low cost; for plastic sludge, a hopper of a continuous double-horizontal-shaft stirrer similar to a stable soil mixer cannot realize continuous and uniform blanking, and cannot ensure accurate metering and doping of an externally doped material; the internal structures of two types of equipment used for plant mixing are suitable for stirring concrete and stable inorganic binder materials, high-viscosity and plastic sludge and a consolidation agent cannot be stirred and mixed uniformly, and the quality of a mixed material cannot be guaranteed.
If the plastic sludge excavated by the underground engineering is to be engineered in a large scale by an improved solidification mode and the improved solidified sludge is recycled for filling and greening, construction equipment with high productivity, high efficiency and good economical efficiency and improved materials and construction processes adapted to the construction equipment must be developed, which is a trend of sludge treatment and is an urgent problem to be solved.
Disclosure of Invention
In view of the above, the invention provides a method for synchronously improving and dewatering sludge excavated in urban rail transit engineering, the sludge treated by the method provided by the invention can be used for engineering, and the treated sludge can be used for filling materials on the bottom layer of a railway foundation bed and a embankment below the foundation bed.
The invention provides a method for synchronously improving and dehydrating sludge excavated in urban rail transit engineering, which comprises the following steps:
s1, slurrying sludge and removing impurities:
most of sludge dug out in urban rail transit engineering is in a soft plastic state, and contains impurities such as uneven massive sludge, construction waste and the like, which are not beneficial to fully mixing improved materials and the sludge and deeply dehydrating a plate-and-frame filter press, so that the sludge needs to be subjected to water slurry adding and impurity removal treatment, and the water content of the obtained slurry is adjusted to 75-90% in the treatment process;
s2, metering, feeding and uniformly mixing:
weighing a modifier, adding water to prepare modifier slurry, adding the prepared modifier slurry into slurry to obtain mixed slurry, uniformly stirring the mixed slurry by using a double-shaft stirrer, and standing for tempering to obtain mixed slurry with the water content of 70-90%; adding modifier slurry after the sludge is slurried, and fully mixing and reacting the modifier slurry and the modifier slurry so as to deeply modify the sludge;
s3, press-filtering and dehydrating the mixed slurry:
performing filter pressing dehydration on the mixed slurry by adopting a plate-and-frame filter press, and quickly reducing the water content of the mixed slurry to obtain a mud cake with the geotechnical water content of 28-35%, namely improved soil; the deep dehydration of the plate-and-frame filter press enables the moisture content of the improved silt to be rapidly reduced and to be close to the optimal moisture content of the silt as soon as possible, and the requirements of paving and rolling construction conditions and application technical indexes are met;
s4, adjusting the water content of the improved soil:
the improved soil obtained by filter pressing dehydration can be transported to a construction position on site or by loading for standing and stacking, and is turned and stirred during the stacking period, so that the geotechnical water content of the improved soil is reduced quickly, and the geotechnical water content is close to the optimal geotechnical water content as soon as possible.
Further, in step S2, the modifier is composed of lime, fly ash, mineral admixture, and inorganic additive; wherein, the mineral admixture selects at least one of ground slag, ground natural zeolite, silica fume and metakaolin, the inorganic additive selects at least one of ferric salt, aluminum salt, polymeric ferric salt and polymeric aluminum salt, the ferric salt can be ferric sulfate, ferric nitrate, ferric chloride and the like, the aluminum salt can be aluminum sulfate, aluminum nitrate, aluminum chloride and the like, the polymeric ferric salt can be polymeric ferric sulfate, polymeric ferric nitrate, polymeric ferric chloride and the like, and the polymeric aluminum salt can be polymeric aluminum sulfate, polymeric aluminum nitrate, polymeric aluminum chloride and the like; lime can be replaced by carbide slag; the lime/carbide slag provides a substantial amount of Ca (OH)2Providing an alkaline environment for the solidification reaction of the sludge, andthe curing reaction is facilitated to occur; the fly ash can improve the grain composition, exert the morphological effect and the volcanic ash activity, and is mixed with Ca (OH)2Chemical reaction is carried out to generate a compound with water hardening gelling performance, and the later strength of the improved soil is improved; the mineral admixture has higher activity with Ca (OH)2The reaction generates a gelled substance, and the early strength of the improved soil is improved; high-valence cations generated after the inorganic additive is dissolved in water have strong ion exchange capacity, and can exchange low-valence cations on the surfaces of clay particles in the slurry, thereby playing the roles of neutralizing surface charges, compressing double electric layers and weakening the repulsion among particles, and being beneficial to the dehydration of the slurry.
Further, in step S2, the weight ratio of the dry matters of the lime, the fly ash, the mineral admixture, the inorganic additive and the slurry is: 6-18: 3-12: 1.5-9: 0.1-2: 100, the improved soil obtained by improvement can meet engineering requirements by strictly controlling the weight ratio of the raw materials.
Further, in the step S2, in the process of adding the modifier slurry into the slurry, the slurry concentration is detected on line by using an ore slurry concentration meter, and the adding proportion of the modifier is ensured by a flow synchronous metering method for adding the modifier; the problems of high pollution, inaccurate metering, uneven mixing, low efficiency and the like in the sludge treatment process can be solved through the process links of front-end impurity removal, online accurate metering and feeding, stirring and uniform mixing and the like.
Further, in the step S3, when filter pressing dehydration is performed by adopting a plate-and-frame filter press, feeding is performed by using a centrifugal pump, wherein the feeding pressure is 0.8-1.0 MPa, and the feeding time is 40-70 min.
Further, in the step S3, the pressing pressure of the plate-and-frame filter press is 1.1-1.3 MPa, and the pressing time is 6-14 min; and the back flushing time is 25-35 s.
Further, in step S4, the standing and stacking time at low temperature in winter is 5 to 10 days, and the standing and stacking time at high temperature in summer is 3 to 7 days.
Compared with the prior art, the invention has the following advantages:
1. the sludge modifier for urban rail transit engineering excavation used by the method provided by the invention has the advantages of strong adaptability, convenience in use and long construction time, the sludge modified by the modifier is greatly improved in engineering performance, the strength of a filling solidified body is high, the durability is good, the technical requirements of the railway foundation bed bottom layer and the embankment filler below the foundation bed can be met, and the urban rail transit engineering excavation sludge modifier has the economic advantage of low price;
2. after the method provided by the invention is used for improving and treating the sludge excavated in the urban rail transit engineering, the improved soil can be transported to a construction part on site or by loading, the water content is reduced by stirring, and the paving and rolling allow more allowance of construction time without affecting the quality; the improved soil can be formed for a long time: the low-temperature forming can be delayed for 5-10 days in winter, the high-temperature forming can be delayed for 3-7 days in summer, the water content of the improved soil naturally drops to meet the paving and rolling construction conditions, the obtained improved soil can be directly used as the railway bed bottom layer and the embankment filler below the bed, the technical problems that the sludge dug out in urban rail transit engineering cannot be reduced, harmlessly, stably and resourcefully treated are solved, the waste can be changed into valuable, the harm is changed into beneficial, the engineering cost is reduced, and the remarkable technical, economic, environmental and ecological benefits are obtained; meanwhile, the method provided by the invention can also be applied to resource and engineering utilization of similar dredging sludge, river and lake sludge and industrial slag sludge, solves the technical problems of the series of the dredging sludge, and creates higher economic benefit and social benefit.
Drawings
FIG. 1 is a schematic flow chart of a method for synchronously improving and dewatering sludge excavated in urban rail transit engineering according to the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described with reference to the accompanying drawings and examples.
In the following examples 1 to 4 and comparative examples 1 to 2, the sludge used was sludge generated during excavation of urban rail transit works, the sludge was in a soft plastic state, and according to the specification of railroad bed design (TB10001 to 2016), the sludge was high liquid limit clay, which belongs to the "D" group filler and cannot be directly used as a bed filler, the related detection results of the sludge are shown in table 1, and the particle analysis results of the sludge are shown in table 2.
Table 1: correlation of the detection results of the sludge used
In the following examples and comparative examples, the moisture content of the earth referred to means the mass of water as a percentage of the mass of dry soil, and the moisture content referred to means the mass of water as a percentage of the total mass of the material.
Example 1:
referring to fig. 1, embodiment 1 provides a method for synchronously improving and dewatering sludge excavated in urban rail transit engineering, including the following steps:
step S1, weighing 65.2kg of sludge with the geotechnical water content of 44.9%, adding 114.8kg of water into the sludge for pulping treatment and removing large-particle impurities to obtain slurry with the water content of 75%.
Step S2, weighing 3.82kg of lime, 2.70kg of fly ash, 1.35kg of ground slag and 0.045kg of aluminum sulfate according to the proportion of 8.5%, 6%, 3% and 0.1% of dry matter of the slurry (the mass of the dry matter in the slurry is equal to that of the dry matter in the sludge in the step S1), adding water into the lime, the fly ash, the ground slag and the aluminum sulfate to prepare corresponding slurry or solution, adding the prepared slurry or solution into the slurry in the step S1 to obtain mixed slurry, stirring the mixed slurry by using a double-shaft stirrer to uniformly mix the mixed slurry, and after stirring, carrying out hardening and tempering reaction on the mixed slurry to obtain mixed slurry with the water content of 70%.
Step S3, performing filter pressing, dehydration and consolidation on the mixed slurry obtained in the step S2 by adopting a plate-and-frame filter press, and rapidly reducing the water content of the mixed slurry to obtain a mud cake with the geotechnical water content of 31%, namely improved soil; the pressing pressure of the plate-and-frame filter press is 1.1MPa, and the pressing time is 8 min; the blowback time was 25 s.
And step S4, the improved soil obtained by dehydration and consolidation is stacked statically and is turned and stirred during the stacking period so as to quicken the reduction of the moisture content of the improved soil, and the moisture content of the improved soil approaches to the optimal moisture content of the soil as soon as possible.
Example 2:
the embodiment 2 provides a method for synchronously improving and dewatering sludge excavated in urban rail transit engineering, which comprises the following steps:
step S1, weighing 65.2kg of sludge with the geotechnical water content of 44.9%, adding 234.8kg of water into the sludge for pulping treatment and removing large-particle impurities to obtain slurry with the water content of 85%.
And S2, weighing 5.18kg of lime, 2.70kg of fly ash, 1.35kg of silica fume and 0.225kg of ferric sulfate according to the proportion of 11.5%, 6%, 3% and 0.5% of dry matter of the slurry respectively, adding water into the lime, the fly ash, the silica fume and the ferric sulfate respectively to prepare corresponding slurry or solution, adding the prepared slurry or solution into the slurry obtained in the step S1 to obtain mixed slurry, stirring by using a double-shaft stirrer to uniformly mix the mixed slurry, and standing, reacting and tempering the mixed slurry after stirring is finished to obtain the mixed slurry with the water content of 75%.
Step S3, performing filter pressing, dehydration and consolidation on the mixed slurry obtained in the step S2 by adopting a plate-and-frame filter press, and rapidly reducing the water content of the mixed slurry to obtain a mud cake with the geotechnical water content of 30%, namely improved soil; the pressing pressure of the plate-and-frame filter press is 1.2MPa, and the pressing time is 7 min; the blowback time was 28 s.
And step S4, the improved soil obtained by dehydration and consolidation is stacked statically and is turned and stirred during the stacking period so as to quicken the reduction of the moisture content of the improved soil and approach the optimal moisture content of the soil as soon as possible.
Example 3:
embodiment 3 provides a method for synchronously improving and dewatering sludge excavated in urban rail transit engineering, which comprises the following steps:
step S1, weighing 65.2kg of sludge with the geotechnical water content of 44.9%, adding 159.8kg of hydrated slurry into the sludge for treatment and removing large-particle impurities to obtain slurry with the water content of 80%.
And S2, weighing 4.05kg of lime, 4.05kg of fly ash, 0.90kg of metakaolin and 0.45kg of polyaluminium chloride according to the proportion of 9%, 2% and 1% of dry matter of the slurry, adding water into the lime, the fly ash, the metakaolin and the polyaluminium chloride respectively to prepare corresponding slurry or solution, adding the prepared slurry or solution into the slurry obtained in the step S1 to obtain mixed slurry, stirring the mixed slurry by using a double-shaft stirrer to uniformly mix the mixed slurry, and standing the mixed slurry after stirring to react and temper to obtain the mixed slurry with the water content of 75%.
Step S3, performing filter pressing, dehydration and consolidation on the mixed slurry obtained in the step S2 by adopting a plate-and-frame filter press, and rapidly reducing the water content of the mixed slurry to obtain a mud cake with the geotechnical water content of 31.7%, namely improved soil; the pressing pressure of the plate-and-frame filter press is 1.2MPa, and the pressing time is 9 min; the blowback time was 30 s.
And step S4, the improved soil obtained by dehydration and consolidation is stacked statically and is turned and stirred during the stacking period so as to quicken the reduction of the moisture content of the improved soil, and the moisture content of the improved soil approaches to the optimal moisture content of the soil as soon as possible.
Example 4:
embodiment 4 provides a method for synchronously improving and dewatering sludge excavated in urban rail transit engineering, comprising the following steps:
step S1, weighing 65.2kg of sludge with the geotechnical water content of 44.9%, adding 199.5kg of water into the sludge for pulping treatment and removing large-particle impurities to obtain slurry with the water content of 83%.
And S2, weighing 4.05kg of carbide slag, 3.15kg of fly ash, 1.80kg of ground natural zeolite and 0.675kg of polymeric ferric chloride according to the proportion of 9%, 7%, 4% and 1.5% of dry matter of the slurry respectively, adding water into the carbide slag, the fly ash, the ground natural zeolite and the polymeric ferric chloride respectively to prepare corresponding slurry or solution, adding the prepared slurry or solution into the slurry obtained in the step S1 to obtain mixed slurry, stirring the mixed slurry by using a double-shaft stirrer to uniformly mix the mixed slurry, and standing, reacting and tempering the mixed slurry after stirring to obtain the mixed slurry with the water content of 75%.
Step S3, performing filter pressing, dehydration and consolidation on the mixed slurry obtained in the step S2 by adopting a plate-and-frame filter press, and rapidly reducing the water content of the mixed slurry to obtain a mud cake with the geotechnical water content of 33%, namely improved soil; the pressing pressure of the plate-and-frame filter press is 1.1MPa, and the pressing time is 10 min; the blowback time was 30 s.
And step S4, the improved soil obtained by dehydration and consolidation is stacked statically and is turned and stirred during the stacking period so as to quicken the reduction of the moisture content of the improved soil, and the moisture content of the improved soil approaches to the optimal moisture content of the soil as soon as possible.
Comparative example 1:
comparative example 1 differs from example 1 only in that: no addition of ground slag; the rest is basically the same as the embodiment 1.
Comparative example 1 obtained a mud cake with a geotechnical water content of 32.1%.
Comparative example 2:
comparative example 2 differs from example 3 in that: the mixing amount of lime and fly ash is different; weighing 2.70kg of lime, 5.18kg of fly ash, 1.35kg of metakaolin and 0.45kg of polyaluminium chloride according to the proportion of 5%, 13%, 2% and 1% of dry matter of the slurry respectively; the rest is basically the same as the embodiment 2.
Comparative example 2 obtained a mud cake with a geotechnical water content of 30.8%.
The results of the measurements of the mud cakes (i.e., improved soils) obtained in examples 1 to 4 and comparative examples 1 to 2 after being left for 4 days while being stirred are shown in Table 3.
Table 3: statistical table of detection results of mud cakes (namely improved soil) after being turned and stirred for 4 days
The 7d saturated unconfined compressive strength of the mud cakes (i.e., the improved soil) obtained in examples 1 to 4 meets the requirements of the chemically improved soil as the foundation bed bottom layer and the embankment filler below the foundation bed in the railway roadbed design specification (TB10001-2016) and the railway roadbed engineering construction quality acceptance standard (TB10414-2018) by taking the railway roadbed design specification (TB10001-2016) and the railway roadbed engineering construction quality acceptance standard (TB10414-2018) as reference bases, wherein the compaction standards of the chemically improved soil as the foundation bed bottom layer and the embankment filler below the foundation bed in the railway roadbed design specification (TB10001-2016) are shown in table 4, and the compaction standards of the chemically improved soil as the foundation bed bottom layer and the embankment filler below the foundation bed in the railway roadbed engineering construction quality acceptance standard (TB10414-2018) are shown in table 5.
Table 4: standard for compaction of bed bottom and embankment filling under bed in design Specification for railroad bed (TB10001-2016)
Table 5: standard for compacting embankment filler under foundation bed and foundation bed by using chemically modified soil in Standard for quality acceptance of engineering construction of railway roadbed (TB10414-2018)
Note: the numerical value in brackets is the strength value required by the chemical improved soil in severe cold areas in consideration of the freeze-thaw cycling action.
The features of the embodiments and embodiments described herein above may be combined with each other without conflict.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A method for synchronously improving and dewatering sludge excavated in urban rail transit engineering is characterized by comprising the following steps:
s1, adding hydrated slurry and removing impurities to the sludge to obtain slurry;
s2, weighing the modifying agent, adding water to prepare modifying agent slurry, adding the prepared modifying agent slurry into the slurry obtained in the step S1 to obtain mixed slurry, uniformly stirring the mixed slurry by using a double-shaft stirrer, and standing and tempering to obtain mixed slurry;
s3, performing filter pressing dehydration on the mixed slurry obtained in the step S2 by adopting a plate-and-frame filter press, and reducing the water content of the mixed slurry to obtain mud cakes, namely improved soil;
and S4, standing and stacking the improved soil obtained in the step S3 on site or transported to a construction site, and turning and stirring the improved soil during stacking so as to further reduce the moisture content of the improved soil.
2. The method for synchronously improving and dewatering the urban rail transit engineering excavation sludge according to claim 1, wherein in step S1, the sludge is sludge generated in the urban rail transit engineering excavation process; the water content of the obtained slurry is 75-90%.
3. The method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering according to claim 1, wherein in the step S2, the improving agent is composed of lime, fly ash, mineral admixture and inorganic additive; wherein the mineral admixture selects at least one of ground slag, ground natural zeolite, silica fume and metakaolin, and the inorganic additive selects at least one of ferric salt, aluminum salt, polymeric ferric salt and polymeric aluminum salt.
4. The method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering according to claim 3, wherein in the step S2, the weight ratio of the dry substances of the lime, the fly ash, the mineral admixture, the inorganic additive and the slurry is as follows: 6-18: 3-12: 1.5-9: 0.1-2: 100.
5. the method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering as claimed in claim 1, wherein in step S2, the concentration of the slurry is detected on line by using a pulp concentration meter during the process of adding the improver slurry into the slurry.
6. The method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering according to claim 1, wherein in the step S2, the water content of the mixed slurry is 70-90%.
7. The method for synchronously improving and dehydrating the excavated sludge in the urban rail transit engineering according to claim 1, wherein in the step S3, when a plate-and-frame filter press is used for filter pressing and dehydration, a centrifugal pump is used for feeding, the feeding pressure is 0.8-1.0 MPa, and the feeding time is 40-70 min.
8. The method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering according to claim 1, wherein in step S3, the pressing pressure of a plate-and-frame filter press is 1.1-1.3 MPa, and the pressing time is 6-14 min; and the back flushing time is 25-35 s.
9. The method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering according to claim 1, wherein in the step S3, the geotechnical moisture content of the mud cake is 28% -35%.
10. The method for synchronously improving and dewatering the excavated sludge of the urban rail transit engineering according to claim 1, wherein in step S4, the standing and stacking time at a low temperature in winter is 5-10 days, and the standing and stacking time at a high temperature in summer is 3-7 days.
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